It is required to accurately predict tsunami as fast as possible, for detecting tsunami at a far distance, and promptly giving an alarm. It is therefore necessary to recognize an accurate wave height value and an accurate flow velocity value of tsunami in real time. As countermeasures for this, the following inventions exist as prior arts. (For example, refer to Non-Patent Literatures 1 to 4 and Patent Literature 1.)
In the technique disclosed in Non-Patent Literature 1, a wave height value is predicted in real time from a flow velocity value obtained from a radar, using a nonlinear shallow water equation, which is a kinetic model of tsunami.
In the technique disclosed in Non-Patent Literature 2, a wave height value is predicted in real time by performing filtering of wave height values considering observation errors from wave height values of a tsunami gauge such as a global positioning system (GPS) buoy that is disposed from a coast toward an offshore.
In the technique disclosed in Patent Literature 1, a tsunami wave source is estimated based on a tsunami wave height observed at an observation position, and a tsunami wave height is estimated from the estimated tsunami wave source.
In the technique disclosed in Non-Patent Literature 3, detection of tsunami that uses an HF radar, and an equation of a relationship between a flow velocity and a wave height of tsunami that is based on a shallow water equation are described.
In the technique disclosed in Non-Patent Literature 4, a method of assimilating a flow velocity observation value of an HF radar with a tidal model is described as an estimation method of a flow velocity in a normal time when tsunami does not exist.